An everting catheter typically includes an outer catheter having an outer catheter lumen and an inner catheter movable longitudinally in the outer catheter lumen and having an inner catheter lumen. An everting element is coupled to the outer catheter and the inner catheter so that, with movement of the inner catheter distally in the outer catheter lumen, the everting element can be everted through an opening in the outer catheter.
An everting catheter of this type can be inserted through a passage in the human body with the everting element in an inverted position. An elongated, flexible instrument can then be introduced through the inner catheter lumen and the everted everting element to position the instrument into a desired body region and accomplish any of a variety of medical procedures and/or viewing of internal body regions.
In order that any of these functions can be properly carried out, it is commonly necessary to know the location of the distal end of the instrument in relation to the distal end of the everting element. This may be necessary, for example, to prevent the instrument from extending distally beyond the everting element where the instrument might cause injury to delicate body tissues or organs.
Prior art techniques for ascertaining the position of the instrument in relation to the distal end of the everting element include ultrasound and fluoroscopy. Unfortunately, neither of these techniques is satisfactory for use in the fallopian tubes. More specifically, ultrasound is uncomfortable for the patient and does not locate the distal end of the instrument in relation to the distal end of the everting element as precisely as desired. In this regard, it is important that the instrument not extend beyond the distal end of the everting element because of the very delicate nature of the fallopian tubes. Fluoroscopy is also not suitable because of the possibility that the X-rays will be detrimental to the patient's fertility.